WIlinus Pass was a mountain pass leading into Uberwald. The road from Ankh-Morpork to Bonk passed through here, and wagons and ox trains frequented the road. As did bandits, at least until Sam Vimes passes through on his way to Bonk to serve as Ankh-Morpork's ambassador. Vimes, Detritus, and Cheery Littlebottom fought them, but it was Inigo Skimmer, an Assassin, who did the most damage. Vimes and the others made their escape, leaving Inigo surrounded by enemies (who cares what happens to a bunch of bandits?). However, he quickly killed all of the bandits and caught up with Vimes by nightfall.
Rumors about this attack in Wilinus Pass spread rapidly through Uberwald, and these rumors all put Vimes as the killer of thirty men and a dog at Wilinus. As a result, Vimes becomes accustomed to hearing whispered phrases like "Wilinus", and "thirty men and a dog" wherever he goes. But also as a result, Vimes finds he has no trouble getting past guards... at least once they know who he is.
The Wilinus Pass was also once the scene of yet another so-called 'Battle of Koom Valley', although Captain Carrot describes this particular one as "more of a fracas".